@mixin bg-image($url){
  background-image: url('image/' + $url + "@2x.png");
  @media (-webkit-min-device-pixel-ratio: 3),(min-device-pixel-ratio: 3){
    background-image: url('image/'+ $url + "@3x.png");
  }
}
@mixin border-1px($color){
  position: relative;
  &:after{
    display: block;
    position: absolute;
    left: 0;
    bottom: 0;
    width: 100%;
    border-top: 1px solid $color;
    content: '';
  }
}
@mixin border-none(){
  position: relative;
  &:after{
    border-top: none;
  }
}
